chore: Add a note about sh dependency

_example/plugin/README.md

@@ -3,7 +3,7 @@
 ### Build
 
 ```bash
-go build main.go
+go build -o plugin_example main.go
 ```
 
 NOTE: protolint plugin is backed by [hashicorp/go-plugin](https://github.com/hashicorp/go-plugin), not the [plugin](https://golang.org/pkg/plugin/) standard library.
@@ -13,5 +13,10 @@ Therefore, you can build the plugin just as a normal Go main package.
 ### Run
 
 ```bash
-protolint -plugin ./your_plugin_binary /path/to/files
+protolint -plugin ./plugin_example /path/to/files
+
+# Or you can pass some flags to your plugin:
+protolint -plugin "./plugin_example -go_style=false" /path/to/files
 ```
+
+NOTE: `sh` must be in your PATH.

_example/plugin/main.go

@@ -1,16 +1,24 @@
 package main
 
 import (
+	"flag"
+
 	"github.com/yoheimuta/protolint/_example/plugin/customrules"
 	"github.com/yoheimuta/protolint/internal/addon/rules"
 	"github.com/yoheimuta/protolint/linter/rule"
 	"github.com/yoheimuta/protolint/plugin"
 )
 
+var (
+	goStyle = flag.Bool("go_style", true, "the comments should follow a golang style")
+)
+
 func main() {
+	flag.Parse()
+
 	plugin.RegisterCustomRules(
 		// The purpose of this line just illustrates that you can implement the same as internal linter rules.
-		rules.NewEnumsHaveCommentRule(true),
+		rules.NewEnumsHaveCommentRule(*goStyle),
 
 		// A common custom rule example. It's simple.
 		customrules.NewEnumNamesLowerSnakeCaseRule(),